1. Field of Invention
The present invention relates to a photopolymerizable composition in which flame-retardant particles are mixed with a photopolymerizable monomer, and a flame-retardant resin-formed article comprising the same. Specifically, the invention relates to a photopolymerizable composition excellent in flame-retardancy, water repellency, oil repellency, heat resistance, environmental resistance, and photopolymerizability, and a flame-retardant resin-formed article comprising the same.
2. Description of the Related Art
In recent years, broadband services such as high speed Internet has become widespread in the information industry. In order to respond to the rapid increase in information capacity required by each home, expectations are rising for optical communications, particularly optical fiber.
Considering the development of WDM (Wavelength Division Multiplexing), optical fiber core wire is most promising to be used as an optical fiber for Fiber to the Home (FTTH), a plan for introducing optical fiber to home terminals, which is scheduled to be laid from now on. As a conventional optical fiber core wire, an optical fiber core wire composed of an optical fiber (glass core wire or polymer core wire), a primary covering material (primary) and a secondary covering material (secondary) having a urethane structure and which cover an optical fiber, and a flame-retardant polyethylene covering material (jacket) constituting an outermost layer has been known.
However, an outermost layer having only a flame-retardant polyethylene jacket is insufficient for flame retardancy of an optical fiber. In addition, conventional primary and secondary covering materials having a urethane structure are extremely inferior in flame retardancy and weather resistance. For this reason, from the viewpoint of flame retardancy and weather resistance, it is difficult to apply currently used optical fiber to FTTH, and a substitute therefor has been demanded. In addition, requirements on flame retardancy and weather resistance are stringent for application in aircrafts and vehicles.
With ever increasing demand for optical fiber, there is an urgency to improve the properties thereof, including flame retardancy, and development has been carried.
As a flame-retardant used for the purpose of making a resin flame-retardant by mixing into the resin, a halogen-based compound, antimony trioxide, a phosphorus-based compound, and a hydrated metal compound (metal hydrate) have previously been used. However, the halogen compound and antimony trioxide are being eliminated due to environmental problems, while the hydrated metal compound is suitable because it can reduce the impact on the environmental, and is also excellent from the viewpoint of resin recycling.
However, since a considerable amount of hydrated metal compound is required in order to obtain equivalent flame retardancy as compared with other organic flame-retardant compounds, it significantly reduces polymer physical properties. In order to realize flame retardancy equivalent to that of the aforementioned other organic flame-retardants without degrading polymer physical properties, a hydrated metal compound having a small particle diameter must be uniformly dispersion-stabilized as a particle unit without being aggregated in a resin. For this reason, when particles consisting of a metal hydrate are mixed into a resin, it is preferable to form a uniform covering layer on a particle surface in order to secure dispersibility in a resin, and prevent an active group from influencing on a resin and damaging the resin properties.
As a method of forming a covering layer on a particle surface, first, surface treatment with higher fatty acid, and formation of a silica layer are known (for example, see Japanese Patent Application Laid-Open (JP-A) Nos.52-30262, 2003-253266). However, when the method is applied to nano-size particles, since particles do not sufficiently disperse under conventional reaction conditions, and covering reaction rate is high, particles undergo covering reaction in the aggregated state and, consequently, uniform covered particles cannot be obtained.
In addition, there is a method of treating a surface of an inorganic powder with polyamino acid, or reacting vapor phase cyclic organosiloxane on the surface (for example, see JP-A Nos.57-145006, 61-268763). However, dispersibility is not assured even in these methods when applied to nano-size particles, and aggregated materials are generated.
In addition, there has been proposed a curing resin composition in which aluminum hydroxide is used as a filler in an ultraviolet-ray curing resin and/or a thermosetting resin (for example, see JP-A No.10-36682). However, in this method, particularly, when a flame-retardant having a large particle diameter is blended in a photocuring resin, light permeability deteriorates during curing, and photocuring property diminished.
Further, there has been proposed a photopolymerizable composition in which a photopolymerizable monomer or oligomer is combined with a water-repellent fused polycyclic compound (for example, see JP-A No.2004-131632). However, since the water-repellent fused polycyclic compound used herein is a halogen compound, the method has a problem from the viewpoint of reducing impact on the environment.
Thus, regarding making a resin flame-retardant by photopolymerization which is indispensable in the aforementioned covering material for optical fiber, technology for obtaining high flame retardancy while maintaining mechanical properties of a resin without causing environmental problems has not been established yet.